1. Field of the Invention
The present invention relates to a disc reproducing apparatus and a disc recording apparatus for use with a magneto-optical disc driving apparatus that includes a memory in order to present a reproduced sound from being interrupted by an external vibration.
2. Description of the Prior Art
CD players are known to reproduce a CD (compact disc) in which digital audio data is recorded on spiral tracks as rows of pits. Upon playback, the CD player reproduces a digital audio data by detecting that a laser beam radiated on and reflected from on the tracks of the disc is changed in intensity due to the existence of pits while rotating the disc at a constant linear velocity.
Under ordinary working conditions, the CD player can reproduce audio data without trouble according to error correction processing using an error detection code and an error correction code.
It is frequently observed that a CD player having an optical pickup cannot correctly reproduce data because the servo system (such as a focusing servo and a tracking servo of the optical system) is disabled by an mechanical external disturbance such as vibration, shock or the like. Such accidents cannot be compensated for even by the above error correction processing. The playback is temporarily interrupted, causing the reproduced sound to be interrupted.
Unlike home CD players of the floor type, a conventional vehicular CD player or portable CD player that tends to be causing the very large vibrations or impulses includes a mechanical vibration isolating mechanism in order to present the reproduced sound from being interrupted. Such a vibration isolating mechanism is not always sufficient and cannot suppress a reproduced sound from being interrupted depending on the magnitude of vibration or impulse.
In order to completely prevent the reproduced sound from being interrupted, it is proposed to prevent a reproduced sound from being interrupted by reading out reproduced data from a semiconductor memory serving as a data buffer of a relatively large capacity. That is, when the servo system such as the focusing servo and the tracking servo of the optical pickup is disabled by the mechanical external disturbance such as vibration, impulse or the like, reproduced data that has been stored in the semiconductor memory until the servo system returns to the normal condition, are sequentially read out to thereby prevent the playback from being interrupted.
In the conventional apparatus, data stored in the semiconductor memory is utilized to present the mechanical external disturbance such as vibration, impulse or the like in the reproduced sound. The storage capacity of the semiconductor memory is limited so that, when the external disturbance takes place several times, a reproduced sound may be interrupted. Therefore, the user cannot discern the reason why the reproduced sound is interrupted, i.e., the reproduced sound might be interrupted because the function of the semiconductor memory is not operated correctly or because the semiconductor memory suffers from a load that exceeds a storage capacity thereof.